A working cylinder without a piston rod is known from Federal Republic of Germany OS 38 07 786 which also refers to U.S. Pat. Nos. 4,664,020 and 4,545,290.
The known device of OS 38 07 786 is provided on a carriage of a working cylinder which serves as the driven part. The carriage is mounted for displacement in a guide arranged in the longitudinal direction of the working cylinder which is formed by a profiled-section pipe. The carriage is further connected via a driver element with a piston which serves as a driving part and which is displaceably or movably arranged and sealed off within the profiled-section pipe.
A part of the carriage which faces the profiled-section pipe extends into a recess extending in the longitudinal direction of the profiled-section pipe, the carriage moving parallel to said recess. The recess is covered by a cover strap. The cover strap is held in a mount which consists of undercuts or grooves which are provided in the lateral walls which define the recess.
In order to be able to thread the cover strap which passes through the carriage out of the recess and to thread the strap again into the recess upon movement of the carriage in the direction of the longitudinal axis of the cylinder, the carriage is provided, in the region of the ends of the part attached to the carriage and in front of and behind the region into which the part attached to the carriage extends into the recess, with inclines for the threading out and in of the cover strap located on the sides of the cover strap facing away from each other, with the inclines extending obliquely to the longitudinal axis of the cover strap, and seen in the direction of the longitudinal axis of the cover strap.
Upon movement of the carriage in the direction of the longitudinal axis of the cylinder, the cover strap is forced out of the recess by the incline serving as a threading-out device which is placed into the side of the cover strap facing the recess. In this process, the projections of the cover strap which are located in the undercuts are pulled out of the undercuts.
The reintroduction of the cover strap is effected by means of the incline serving as a threading-in device which lies on the cover strap on the side thereof facing away from the recess and forces the projections of the cover strap into the undercuts in the walls defining the recess.
This working cylinder has the disadvantage that both upon the threading of the cover strap out of the recess and upon the threading thereof into the recess relatively large forces of deformation occur on the cover strap and furthermore relatively large frictional forces also occur between the projections of the cover strap and the walls defining the undercuts causing a considerable amount of wear on the projections of the cover strap.
Furthermore, the cover strap must consist of a material which is of relatively high elasticity.